[PATCH] fb: sh-mobile: Fix deadlock risk between lock_fb_info() and console_lock()

Bruno Prémont
2011-09-02T17:24:55Z

Following on Herton's patch "fb: avoid possible deadlock caused by
fb_set_suspend" which moves lock_fb_info() out of fb_set_suspend()
to its callers, correct sh-mobile's locking around call to
fb_set_suspend() and the same sort of deaklocks with console_lock()
due to order of taking the lock.

console_lock() must be taken while fb_info is already locked and fb_info
must be locked while calling fb_set_suspend().

Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
---

Hi Florian,

> On the other hand I just noticed the original patch didn't have
> Bruno's Signed-off and a commit message was missing. So may I ask you,
> Bruno, to add your Signed-off or preferably resend the version tested
> by Guennadi in the appropriate patch format.

Here it is with commit message and the Signed-off-by's.

Thanks,
Bruno

drivers/video/sh_mobile_hdmi.c | 47 ++++++++++++++++++++++-----------------
1 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/drivers/video/sh_mobile_hdmi.c b/drivers/video/sh_mobile_hdmi.c
index 7d54e2c..647ba98 100644
--- a/drivers/video/sh_mobile_hdmi.c
+++ b/drivers/video/sh_mobile_hdmi.c
@@ -1111,6 +1111,7 @@ static long sh_hdmi_clk_configure(struct sh_hdmi *hdmi, unsigned long hdmi_rate,
static void sh_hdmi_edid_work_fn(struct work_struct *work)
{
struct sh_hdmi *hdmi = container_of(work, struct sh_hdmi, edid_work.work);
+ struct fb_info *info;
struct sh_mobile_hdmi_info *pdata = hdmi->dev->platform_data;
struct sh_mobile_lcdc_chan *ch;
int ret;
@@ -1123,8 +1124,9 @@ static void sh_hdmi_edid_work_fn(struct work_struct *work)

mutex_lock(&hdmi->mutex);

+ info = hdmi->info;
+
if (hdmi->hp_state == HDMI_HOTPLUG_CONNECTED) {
- struct fb_info *info = hdmi->info;
unsigned long parent_rate = 0, hdmi_rate;

ret = sh_hdmi_read_edid(hdmi, &hdmi_rate, &parent_rate);
@@ -1148,42 +1150,45 @@ static void sh_hdmi_edid_work_fn(struct work_struct *work)

ch = info->par;

- console_lock();
+ if (lock_fb_info(info)) {
+ console_lock();

- /* HDMI plug in */
- if (!sh_hdmi_must_reconfigure(hdmi) &&
- info->state == FBINFO_STATE_RUNNING) {
- /*
- * First activation with the default monitor - just turn
- * on, if we run a resume here, the logo disappears
- */
- if (lock_fb_info(info)) {
+ /* HDMI plug in */
+ if (!sh_hdmi_must_reconfigure(hdmi) &&
+ info->state == FBINFO_STATE_RUNNING) {
+ /*
+ * First activation with the default monitor - just turn
+ * on, if we run a resume here, the logo disappears
+ */
info->var.width = hdmi->var.width;
info->var.height = hdmi->var.height;
sh_hdmi_display_on(hdmi, info);
- unlock_fb_info(info);
+ } else {
+ /* New monitor or have to wake up */
+ fb_set_suspend(info, 0);
}
- } else {
- /* New monitor or have to wake up */
- fb_set_suspend(info, 0);
- }

- console_unlock();
+ console_unlock();
+ unlock_fb_info(info);
+ }
} else {
ret = 0;
- if (!hdmi->info)
+ if (!info)
goto out;

hdmi->monspec.modedb_len = 0;
fb_destroy_modedb(hdmi->monspec.modedb);
hdmi->monspec.modedb = NULL;

- console_lock();
+ if (lock_fb_info(info)) {
+ console_lock();

- /* HDMI disconnect */
- fb_set_suspend(hdmi->info, 1);
+ /* HDMI disconnect */
+ fb_set_suspend(info, 1);

- console_unlock();
+ console_unlock();
+ unlock_fb_info(info);
+ }
}